.container {
    width: 500px;
    height: 100%;
    margin: 200px auto 0;
}

.envelope {
    position: relative;
    width: 500px;
    height: 300px;
    background: url(../images/bg.png);
    border: 1px #eae1d5 solid;
}
.top {
    background: #837362;
    border-radius: 40px 40px 0 0;
    border: 35px solid rgba(255, 255, 255, 0.1);
    border-bottom: none;
    box-shadow: inset 0 10px 30px 10px rgba(0, 0, 0, 0.1);
    position: absolute;
    top: -35px;
    width: calc(100% - 70px);
    z-index: 1;
}
.bottom {
    background: url(../images/bg.png);
    width: 100%;
    height: 65%;
    position: absolute;
    left: 0;
    bottom: 0;
    z-index: 3;
    border: 1px #eae1d5 solid;
    box-shadow: inset 0 0 10px 1px rgba(255, 255, 255, 0.6), 0 -2px 4px -3px rgba(0, 0, 0, 0.75), 0 2px 3px -2px rgba(0, 0, 0, 0.6);
}


.front {
    transform: rotateY(180deg);
    background: #837362;
    box-shadow: inset 0 10px 30px -10px rgba(0, 0, 0, 0.3), inset 0 1px 0 rgba(0, 0, 0, 0.2), inset 0 2px 0 rgba(255, 255, 255, 0.2);
    border-bottom-right-radius: 40px;
    border-bottom-left-radius: 40px;
    position: absolute;
    width: 100%;
    height: 100%;
}
.content {
    background: #fafafa;
    width: 60%;
    z-index: 2;
    height: 323px;
    position: absolute;
    left: 20%;
    top: -100px;
    text-align: center;
    user-select: none;
    padding: 9px;
}
span {
    font-size: 20px;
    color: #837362;
    /* TODO：补充下面的代码 */
}
p {
    color: #837362;
    /* TODO：补充下面的代码 */
}